This research program is involved with an investigation of reproduction, oogenesis, and early embryonic development and with the molecular mechanisms that control genetic activity. A variety of methods and living systems continue to be utilized with emphasis on the sea urchin. We will continue to investigate the sequence characteristics of RNA synthesized during oogenesis and stored in the egg and the RNA synthesized during development, both nuclear RNA and polysomal messenger RNA. The modulation of populations of messenger RNA has been observed and will be followed up with an examination of the history of individual messages and their production during oogenesis as well as later, in development. Specific tests are being carried out to determine the role of the repetitive sequences adjacent to structural genes and their transcripts in cellular RNAs.